N-(3-Fluoro-2-phosphonomethoxypropyl) derivatives of heterocyclic purine and pyrimidine bases (FPMP-derivatives) occupy a significant place among compounds effective against retro-viruses causing serious illnesses in man and animals. Under in vitro conditions, these compounds exhibit biological parameters (selectivity of action) better than e.g. 9-(2-phosphonomethoxyethyl)adenine (R. Pauwels, J. Balzarini, D. Schols , M. Baba, J. Desmyter, I. Rosenberg, A. Holy, E. De Clercq: Antimicrob. Ag. Chemother. 32, 1025 (1988)). The said derivatives were hitherto accessible from N-(3-fluoro-2-hydroxypropyl) derivatives of purine or pyrimidine bases (prepared e.g. according to CS-patent application PV 2047-90) by reaction with dialkyl p-toluenesulfonyloxymethanesulfonates or methanesulfonyloxymethanephosphonates in the presence of sodium hydride and subsequent removal of the protecting groups by acid or alkaline hydrolysis and finally with bromotrimethylsilane. The drawback of this method (according to CS-patent application PV 2047-90) is that it is necessary first to prepare the optically active N-(3-fluoro-2hydroxypropyl) derivatives and perform their multistage protection. Another possible solution would be condensation of the heterocyclic base (its silyl derivative or alkali metal salt) with a suitable optically active organophosphorus synthon that has a preformed structure of the side chain of FPMP derivatives. Such a reaction of suitably protected derivatives of glycerol with dialkyl esters of p-toluenesulfonyloxymethanephosphonic acid, followed by partial deblocking and introduction of the reactive tosyl or mesyl group has been utilized e.g. in producing analogous N-(3-hydroxy-2-phosphonomethoxypropyl) derivatives (J. J. Bronson, I. Ghazzouli , M. J. M. Hitchcock, R. R. Webb, J. C. Martin: J. Med. Chem. 32, 1457 (1989)). Still another approach made use of introduction of the esterified phosphonomethyl ether functionality on the hydroxyl component via an acetoxymethyl ether by treatment with bromotrimethylsilane and trialkyl phosphite (CS-patent application PV 3871-90).